When constructing a home or a facility, it is well known to provide access barriers, such as garage doors, which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable access barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. In order to open and close the door, the operator is configured to receive command input signals from a wireless portable remote transmitter, a wired or wireless wall station, a keyless entry device or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
To assist in moving the garage door or movable barrier between limit positions, it is well known to use a remote radio frequency (RF) or infrared transmitter to actuate the motor and move the door in the desired direction. These remote devices allow for users to open and close garage doors without getting out of their car. These remote devices may also be provided with additional features such as the ability to control multiple doors, lights associated with the operators, and other security features. As is well documented in the art, the remote devices and operators may be provided with encrypted codes that change after every operation cycle so as to make it virtually impossible to “steal” a code and use it at a later time for illegal purposes. An operation cycle may include opening and closing of the barrier, turning on and off a light that is connected to the operator and so on.
Although remote transmitters and like devices are convenient and work well, the remote transmitters sometimes become lost, misplaced or broken. In particular, the switch mechanism of the remote device typically becomes worn after a period of time and requires replacement. To overcome this disadvantage, “hands-free” operation of the remote transmitter has been developed in a number of different forms. Generally, “hands-free” means that a user is not required to initiate physical contact with the transmitter or switch to cause some other physical activity, such as movement of a garage door. Such prior art hands-free systems comprise a mobile transmitter that communicates, via various mobile signals, with a base operator that is configured to actuate an access barrier, such as a garage door, between open and closed positions. In some hands-free systems, only the mobile transmitter may generate signals that are received and acted upon by the base operator. In any event, the mobile transmitter is generally carried by a carrying device, such as a vehicle. During operation, the mobile transmitter is configured to transmit mobile signals to the base operator so as to move the access barrier between open and closed positions, depending on the relative position of the carrying device to the base operator and other criteria. Because the operation of the hands-free system requires mobile signals to be generated by the mobile transmitter for a period of time following the activation and deactivation of the carrying device, the hands-free system, in one aspect, sends the mobile signals continuously at all times. However, to increase the convenience of the system, prior art systems contemplated the utilization of an activity sensor that comprises a vibration or noise detection sensor, which monitors when the vehicle that carries the mobile transmitter is started or turned off. By monitoring such phenomena, the activity sensor is able to selectively turn the mobile transmitter on and off in the hope of conserving the battery power used to operate the mobile transmitter. However, such sensors are expensive and susceptible to becoming active by proximity to other noises or vibrations not associated with the carrying device.
One possible solution to conserving battery power is disclosed in U.S. patent application Ser. No. 10/962,224, assigned to the assignee of the present application and incorporated herein by reference. The '224 application discloses a specific embodiment wherein the mobile transmitter is directly connected to the ignition system and power source of the carrying device. However, such an embodiment requires a specialized installation and does not permit easy transfer of the transmitter between carrying devices. And the known hands-free devices all require periodic transmission of a radio frequency signal from the garage door operator. It is believed that this may lead to increased electrical “noise” pollution, which adversely affects nearby electrical communication devices.
In any event, current activity sensors used by the mobile transmitter may be inadvertently triggered by external phenomena other than that generated by the carrying device, such as a vehicle, that is carrying the mobile transmitter. For example, the vibration generated from the acoustic sound waves from a vehicle's sound system may be sufficient to trigger vibration sensors that comprise the activity sensors that comprise the activity sensors. Additionally, because of the significant amount of electrical leakage and electromagnetic interference (EMI) generated by all electronic devices, the potential is also great that the noise sensor may also be inadvertently triggered, thus causing the power supply of the mobile transmitter to be prematurely drained. Furthermore, mobile transmitters that continuously transmit mobile signals tend to rapidly exhaust their power capacity, thus necessitating the frequent and inconvenient change of batteries or recharge thereof.
Therefore, there is a need in the art for a system that automatically moves access barriers depending upon the proximity of a device carrying a remote mobile transmitter, wherein the transmitter automatically emits somewhat periodic signals that are received by the operator, which then moves the barrier and ignores subsequent transmitter signals for a predetermined period of time. Additionally, there is a need for a mobile transmitter that utilizes a motion detector such as an accelerometer that is not adversely affected by vibration or noise. In addition, there is a need for a mobile transmitter that utilizes a motion detector to detect when the carrying device is accelerating or decelerating. Furthermore, there is a need for a mobile transmitter that utilizes a 1-, 2-, or 3-axis accelerometer to ascertain when the carrying device is moving in at least one axis of motion.